In order to be able to allow safe, easy and precise operation of a large-scale manipulator, the prior art proposes measuring the relative instantaneous folding angle of the individual boom segments, for example to determine the folded state of the folding boom, the damping of boom oscillations, load torque limitation or coordinate control. A large number of measuring methods that are suitable for this purpose are known from the prior art.
The folding angle can be sensed for example by mechanical rotation angle measuring systems. However, this is frequently too imprecise or too expensive. In particular, such sensing of the folding angle is difficult when, in the case of a large-scale manipulator of a thick matter pump, a thick matter delivery pipe is guided through the folding joints. Mechanical measurement with a rotation angle meter is only possible when additional mechanical deflection mechanisms are installed.
In addition, it is also known, for angle measurement, to measure the linear deflection of the drive units with which the boom segments are pivoted with respect to a respectively adjacent segment or with respect to the turntable, and to convert the measured deflection into the associated rotation angle of the joint.
However, a disadvantage here is that inaccuracies frequently occur on account of the conversion. Furthermore, the requisite measuring arrangement is complicated.
In order to sense the folding angle, angle sensors based on rotary potentiometers are also known. Potentiometer measurement converts rotary movements into a resistance value and has the advantage that an absolute value is available immediately after switching on. However, a disadvantage here is the mechanical wear. This changes the resistance over time and thus the measurement results are distorted. Also, with such measurements, any misalignment of the components with respect to one another is tolerable only to a very limited extent.
In order to make angle measurement more robust, inclination sensors are used in the prior art. However, a disadvantage here is that the inclination sensors also take into account the sag of the boom segments. This is disadvantageous in particular when, during the folding up of the folding boom for the driving mode of the truck-mounted concrete pump, the closing angle has to be determined. Furthermore, inclination sensors are expensive and, at the beginning of each measurement, it is absolutely necessary to calibrate the sensors. As a result, the use of inclination sensors is very complicated.